Question2Answer - A Q&A site helps an online community to share knowledge.
Community Questions for Confluence - Keep questions and answers in one place with an engaging, community-driven Q&A discussion forum, powered by Confluence
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Stack Overflow for Teams - Everything you love about Stack Overflow in a private space.
Askalot - Askalot is a next generation CQA (Community Question and Answer) system.